For example, the following methods have been reported as methods for producing substituted fluoroolefins.
Non-Patent Document 1 discloses a method for first converting a carbon-halogen (C—X) bond of CF2═CFX (X: halogen atom other than fluorine atom) into a carbon-lithium (C—Li) bond by butyllithium, and then performing C—C bond forming reaction.
Non-Patent Documents 2 and 3 disclose a method for further converting Li of the carbon-lithium (C—Li) bond formed as above into a metal such as Sn, Si, or the like, and then performing C—C bond forming reaction.
However, these methods are not regarded as practical because CF2═CFX used as a raw material is not easily obtainable and relatively expensive. Further, because the fluorine-containing lithium reagent containing the C—Li bond formed at the first stage is very unstable, it is necessary to conduct the reaction under a low temperature of about −100° C.
Non-Patent Documents 4 to 6 disclose a method of reacting tetrafluoroethylene (TFE) with an organic lithium reagent or an aryl magnesium reagent, thereby selectively substituting a fluorine atom. Ph represents phenyl.    PhLi+CF2═CF2→PhCF═CF2 (Non-Patent Document 4)    PhMgBr+CF2═CF2→PhCF═CF2 (Non-Patent Documents 5 and 6)
To ensure desired selectivity in obtaining a desired product from TFE, it is necessary to perform the reaction at a low temperature using a large excess of TFE. When the reaction temperature increases, the progress of the reaction becomes out of control, thereby producing a mixture of 1,2-adducts, products with a larger number of substituents, etc. Consequently, the yield of the desired product greatly decreases.
Non-Patent Document 7 discloses a method of reacting HFC134a (CF3CFH2) with alkyl lithium and generating a fluorine-containing vinyl lithium by elimination reaction. The resulting fluorine-containing vinyl lithium is then subjected to coupling reaction using a vinyl zinc reagent generated by metal replacement using zinc.
However, this method requires an excess amount of expensive alkyl lithium and also suffers from a difficulty in reaction temperature control due to the instability of the fluorine-containing vinyl lithium produced as an intermediate.
In contrast to these known methods, if it is possible to substitute a fluorine atom (F) bonded to the sp2 hybridized carbon atom in the molecule with an organic group using tetrafluoroethylene (TFE), hexafluoropropene (HFP), etc., which are industrially readily obtainable, in the presence of catalyst such as a transition metal substituent, the method is useful for synthesis of substituted fluoroolefins.
Generally, although many methods for introducing a substituent into a nonfluorinated olefin using a transition metal as a catalyst have been reported in the past, only a few methods perform a reaction that activates a C—F bond in a fluoroolefin, and then generate a C—C bond. This is presumably because the binding energy of the C—F bond in the fluoroolefin is much higher than the C—Y (Y represents Cl, Br, I, or the like) bond of other halogen-containing olefins, and also because the fluorine atom, which is small and hard, makes it difficult to cause cleavage of the C—F bond or oxidative addition reaction of metals with respect to the C—F bond. Moreover, there have been no reports of a catalytic reaction to substitute a fluorine atom (F) of a fluoroolefin with an organic group using a transition metal.
A 1-substituted fluoroolefin, such as 1,1,2-trifluorostyrene is useful for, for example, materials of polyelectrolyte. Further, 1,1-disubstituted fluoroolefin, such as 1,1-difluoro-2,2-diphenylethylene, is useful for, for example, medicinal products such as an enzyme inhibitors or ferroelectric materials. However, a method for easily and efficiently producing these compounds has not been established.
For example, Non-Patent Document 8 reports that a 1,1-disubstituted fluoroolefin can be produced by a difluoromethylenation reaction through a Wittig reaction of a carbonyl compound. However, when ketone is used as a carbonyl compound, the yield is low even with an excess amount of Wittig reagent (at least 4 to 5 equivalents). Further, this method also requires a cancer-causing hexamethylphosphorous triamide as a phosphorous compound. As such, the method has several disadvantages.
Therefore, if it is possible to easily produce substituted fluoroolefin (such as, 1-substituted fluoroolefin, 1,1-disubstituted fluoroolefin, or the like) from a readily obtainable fluoroolefin such as TFE, the method can be very useful as a synthetic method.